Omnidirectional wheels and associated wheel guards

ABSTRACT

Technology is provided for omnidirectional wheels having rolling surfaces configured to roll over obstacles when the wheel is moving sideways with respect to its axis of rotation. The omnidirectional wheel can include a central disk assembly and a pair of lateral disk assemblies coaxially positioned on opposite sides of the central disk assembly. The central disk assembly can include a central carrier plate having a first diameter and a plurality of central rollers each rotatably coupled to a circumferential margin of the central carrier plate for rotation about a first roller axis oriented orthogonal to an axis of the wheel. Each lateral disk assembly can include a lateral carrier plate having a second diameter smaller than the first diameter and a plurality of lateral rollers each rotatably coupled to a circumferential margin of the lateral carrier plate for rotation about a second roller axis oriented orthogonal to the wheel axis.

TECHNICAL FIELD

This patent application is directed to wheels for use in holonomicdrivetrains and, more specifically, to omnidirectional wheels andassociated wheel guards.

BACKGROUND

A holonomic drivetrain moves with three degrees of freedom which canprovide enhanced maneuverability for various wheeled vehicleapplications, particularly robotic applications. Holonomic drivetrainstypically use omnidirectional wheels, including mecanum wheels, whichfacilitate shifting the vehicle from side to side or strafing diagonallywithout changing the direction of its wheels. While these maneuvers canprovide advantages from a maneuverability perspective, they can haveproblems negotiating bumps when the wheels move parallel to their axisof rotation and the sides of the wheels can catch on steps and othersurface discontinuities.

BRIEF DESCRIPTION OF THE DRAWINGS

Embodiments of the omnidirectional wheels and associated wheel guardsdescribed herein may be better understood by referring to the followingDetailed Description in conjunction with the accompanying drawings, inwhich like reference numerals indicate identical or functionally similarelements:

FIG. 1 is a side view in elevation of an omnidirectional wheel accordingto a representative embodiment of the present technology.

FIG. 2 is a front view of the omnidirectional wheel shown in FIG. 1.

FIG. 3 is an isometric view of a tapered mecanum wheel according to arepresentative embodiment of the present technology.

FIG. 4A is a side view of the mecanum wheel shown in FIG. 3.

FIG. 4B is a top view of the mecanum wheel shown in FIG. 4A.

FIG. 5 is a diagrammatic top view of a wheeled vehicle incorporating themecanum wheel shown in FIGS. 3-4B.

FIG. 6 is a diagrammatic front view of the wheeled vehicle shown in FIG.5.

FIG. 7 is a diagrammatic front view of a wheeled vehicle illustrating analternative wheel mounting arrangement.

FIG. 8 is a diagrammatic side view of a wheel guard according to arepresentative embodiment of the present technology.

FIG. 9 is an isometric view of the wheel guard shown in FIG. 8.

FIG. 10 is a diagrammatic side view of a wheel guard assembly accordingto another representative embodiment.

The headings provided herein are for convenience only and do notnecessarily affect the scope or meaning of the claimed embodiments.Further, the drawings have not necessarily been drawn to scale. Forexample, the dimensions of some of the elements in the figures may beexpanded or reduced to help improve the understanding of theembodiments. Moreover, while the disclosed technology is amenable tovarious modifications and alternative forms, specific embodiments havebeen shown by way of example in the drawings and are described in detailbelow. The intention, however, is not to unnecessarily limit theembodiments described. On the contrary, the embodiments are intended tocover all suitable modifications, equivalents, and alternatives fallingwithin the scope of the embodiments as defined by the appended claims.

DETAILED DESCRIPTION Overview

Technology is provided for omnidirectional wheels having rollingsurfaces configured to roll over obstacles when the wheel is movingparallel with respect to its axis of rotation. In a representativeembodiment, an omnidirectional wheel can comprise a central diskassembly and a pair of lateral disk assemblies coaxially positioned onopposite sides of the central disk assembly. The central disk assemblycan include a central carrier plate having a first diameter and aplurality of central rollers each rotatably coupled to a circumferentialmargin of the central carrier plate for rotation about a first rolleraxis oriented orthogonal to an axis of the wheel. Each lateral diskassembly can include a lateral carrier plate having a second diametersmaller than the first diameter and a plurality of lateral rollers eachrotatably coupled to a circumferential margin of the lateral carrierplate for rotation about a second roller axis oriented orthogonal to thewheel axis. The smaller diameter of the lateral carrier plates allowsthe disclosed wheels to more easily roll over obstacles.

Technology is also provided for mecanum wheels having tapered rollingsurfaces which can provide advantages over conventional straight mecanumwheels. The disclosed tapered mecanum wheels can be mounted withnegative camber to lower the center of gravity of a wheeled vehicle,such as a robot, or they can be mounted with positive camber to increasethe clearance of the vehicle. In a representative embodiment, a mecanumwheel can comprise a first hub disk having a first diameter and aplurality of first roller mounts disposed around a circumferentialmargin of the first hub disk and a second hub disk having a seconddiameter smaller than the first diameter and a plurality of secondroller mounts disposed around a circumferential margin of the second hubdisk. A plurality of rollers each extends between correspondingcircumferentially offset first and second roller mounts, whereby each ofthe plurality of rollers is mounted for rotation about a correspondingroller axis oriented at a compound angle with respect to the wheel axis.

Technology is provided for wheel guards that can help lift the wheel ofa wheeled vehicle, such as a robot, up and over an obstacle (e.g., abump or step). In an embodiment, a wheel guard can comprise a guard bodyhaving a base portion mountable to a chassis of the wheeled vehicle. Awheel opening can be centrally located in the guard body and configuredto receive a wheel of the wheeled vehicle therethrough. One or moreramped surfaces can extend from the base portion to the wheel opening.In some embodiments, the ramped surfaces extend arcuately between thebase portion and the opening.

In another embodiment, a wheel guard assembly can comprise a guardmember including a ramped surface extending between a first end portionand a second end portion, the second end portion coupleable to asuspension of a wheel of the wheeled vehicle. A pivot mechanism isattached to the first end portion that is coupleable to a chassis of thewheeled vehicle, whereby the guard member can pivot with respect to thechassis as the wheel moves up and down.

General Description

Various examples of the devices introduced above will now be describedin further detail. The following description provides specific detailsfor a thorough understanding and enabling description of these examples.One skilled in the relevant art will understand, however, that thetechniques discussed herein may be practiced without many of thesedetails. Likewise, one skilled in the relevant art will also understandthat the technology can include many other features not described indetail herein. Additionally, some well-known structures or functions maynot be shown or described in detail below so as to avoid unnecessarilyobscuring the relevant description.

The terminology used below is to be interpreted in its broadestreasonable manner, even though it is being used in conjunction with adetailed description of some specific examples of the embodiments.Indeed, some terms may even be emphasized below; however, anyterminology intended to be interpreted in any restricted manner will beovertly and specifically defined as such in this section.

FIGS. 1 and 2 illustrate an omnidirectional wheel 100 according to arepresentative embodiment of the present technology. The omnidirectionalwheel 100 is mountable for rotation about a wheel axis A_(W). In someembodiments, the wheel 100 includes a central disk assembly 102 and apair of lateral disk assemblies 104 coaxially positioned on oppositesides of the central disk assembly 102.

The central disk assembly 102 includes a central carrier plate 106having a central (e.g., first) diameter D_(C). A plurality of centralrollers 108 are rotatably coupled to a circumferential margin of thecentral carrier plate 106 for rotation about a first roller axis A_(RC)oriented orthogonal to the wheel axis A_(W). Each lateral disk assembly104 includes a lateral carrier plate 110 having a lateral (e.g., second)diameter D_(L) smaller than the central diameter D_(C). In someembodiments, the lateral diameters D_(L) of the lateral carrier plates110 can be equal, or can be different from each other. A plurality oflateral rollers 112 are each rotatably coupled to a circumferentialmargin of the lateral carrier plate 110 for rotation about a secondroller axis A_(RL) oriented orthogonal to the wheel axis A_(W). Withreference to FIG. 2, it can be understood that the smaller diameter ofthe lateral carrier plates 106 provides an approach angle Z that allowsthe wheel 100 to roll over obstacles when the wheel is traveling in alateral direction generally parallel to the wheel axis A_(W).

In some embodiments, the circumferential margins of the central andlateral carrier plates 106 and 110, respectively, each include aplurality of notches configured to receive a corresponding roller. Forexample, the lateral carrier plates 110 each includes a plurality ofnotches 114, each of which corresponds to an associated lateral roller112.

In some embodiments, the wheel 100 further comprises a hub 116, whereinthe pair of lateral carrier plates 110 and the central carrier plate 106are attached to the hub 116. In some embodiments, the hub 116 caninclude an axle bore 118 extending along the wheel axis A_(W).

In some embodiments, the lateral rollers 112 are circumferentiallyoffset from the central rollers 108 as shown in the figures. In otherwords, the central rollers 108 and the lateral rollers 112 areinterlaced with each other. In some embodiments, the lateral rollers 112and the central rollers 108 each have approximately the same rollerdiameter. However, in other embodiments the rollers can have differingsizes.

In at least one representative embodiment, the central carrier plate106, the lateral carrier plates 110, and the hub 116 can comprise asingle unitary hub. The unitary hub can have a central disk portion(e.g., 106) with a central diameter and first and second lateral diskportions (e.g., 110) having first and second diameters smaller than thecentral diameter. In some embodiments, the first and second diameters ofthe lateral disk portions can be equal, or can be different from eachother.

Although the omnidirectional wheel 100 is illustrated and describedherein as including a central disk assembly 102 with two lateral diskassemblies 104 having smaller diameters, more or fewer disk assemblieshaving various diameters may be used together in various combinationswithout deviating from the scope of the present technology.

FIG. 3 illustrates a tapered mecanum wheel 200 according to arepresentative embodiment of the present technology. The mecanum wheel200 has a tapered rolling surface 202 which can provide advantages overconventional straight mecanum wheels as described more fully below. Themecanum wheel 200 is mountable for rotation about a wheel axis A_(W).The mecanum wheel 200 can include a first hub disk 204 having a firstdiameter D₁ (FIG. 4A) and a plurality of first roller mounts 206disposed around a circumferential margin of the first hub disk 204. Asecond hub disk 210 having a second diameter D₂ (FIG. 4A) smaller thanthe first diameter D₁ is axially offset from the first hub disk 204. Aplurality of second roller mounts 212 are disposed around acircumferential margin of the second hub disk 210.

A plurality of rollers 220 each extend between correspondingcircumferentially offset first and second roller mounts 206 and 212. Theroller 220*, for example, is mounted for rotation about a roller axisA_(R) oriented at an angle with respect to both planes P₁ and P₂, whichintersect orthogonally along the wheel axis A_(W). As shown in FIG. 4A(side view), the roller axis A_(R) is oriented at an angle X withrespect to plane P₁. As shown in FIG. 4B (top view), the roller axisA_(R) is also oriented at an angle Y with respect to plane P₂.Therefore, each of the plurality of rollers 220 is mounted for rotationabout a corresponding roller axis A_(R) oriented at a compound anglewith respect to the wheel axis A_(W). In contrast, a conventionalmecanum wheel has a flat rolling surface. Accordingly, the roller axisof a conventional mecanum wheel would be oriented at an angle withrespect to only plane P₁ and it would be parallel to plane P₂. Thus, ina conventional mecanum wheel, angle Y is zero.

In some embodiments, angles X and Y can be approximately 45 degrees, forexample. As shown in FIG. 4B, in some embodiments, each of the pluralityof rollers 220 can be tapered from a large end 222 (coupled to acorresponding one of the first roller mounts 206) to a small end 224(coupled to a corresponding one of the second roller mounts 212).

FIG. 5 represents a wheeled vehicle (e.g., a robot) 300 with a mecanumwheel 200, as described above, positioned at each corner of the robot'schassis 302. When viewed from the front, as in FIG. 6, the wheels 200are mounted on the chassis 302 with their rolling surfaces 202 levelwith the ground and their smaller diameter hub 210 facing the chassis302. Thus, the wheels 200 have negative camber with respect to thechassis 302. This wheel arrangement provides the advantage of reducingthe distance B₁ between the robot's center of gravity and the ground,but with less ground clearance C₁. In an alternative arrangement, asshown in FIG. 7, a robot 310 includes wheels 200 mounted on a chassis304 with the their rolling surfaces 202 level with the ground and theirlarger diameter hub 204 facing the chassis 304. Thus, the wheels 200have positive camber with respect to the chassis 304. This wheelarrangement provides the advantage of increasing the ground clearanceC₂, but with an increased distance B₂ between the robot's center ofgravity and the ground. Depending on the application, the wheels 200 canbe oriented with either positive or negative camber to increase therobot's ground clearance or lower the robot's center of gravity.

FIG. 8 illustrates a wheel guard 410 according to a representativeembodiment of the present technology. The wheel guard 410 is disposed onthe bottom or underside of a wheeled vehicle, such as a robot 400 aroundone of its wheels 404. The wheel guard 410 attaches to the robot'schassis 402 and can help lift the robot 400, up and over an obstacle 10(e.g., a bump or step). As shown in FIG. 9, the wheel guard 410 includesa guard body 411 having a base portion 412 mountable to the underside ofa chassis 402 of the wheeled vehicle 400 (FIG. 8) and a wheel opening414 centrally located in the guard body 411. The wheel opening 414 isconfigured to receive the wheel 404 therethrough. One or more rampedsurfaces 416 can extend from the base portion 412 to the wheel opening414. In some embodiments, the wheel opening 414 can be square orrectangular, for example. In some embodiments the base portion 412 canalso be square or rectangular such that the guard body 411 is in theform of a frustum. In other embodiments, the base portion 412 can becircular. In some embodiments, the one or more ramped surfaces 416 canextend arcuately from the base portion 412 to the wheel opening 414 asshown in FIG. 9. In some embodiments, the guard body includes at leastone ramped surface facing the direction of the wheel's axis of rotation.In other embodiments, the guard body includes at least one rampedsurface facing transverse to the direction of the wheel's axis ofrotation. In at least one representative embodiment, the guard body caninclude a pair of oppositely facing ramped surfaces, each facing thedirection of the wheel's axis of rotation.

FIG. 10 illustrates a wheel guard assembly 460 according to anotherrepresentative embodiment. The wheel guard assembly 460 can include twoguard members 462 and 464, each having a ramped surface 472 and 474,respectively. The guard members each extend between a first end portionand a second end portion. The second end portion of each guard member iscoupleable to a suspension 456 of a corresponding wheel 454. The pivotmechanisms 466 and 468 (e.g., hinges) are attached to the first endportions of the guard members 462 and 464, respectively. The pivotmechanisms 466 and 468 are coupleable to the chassis 452 of the wheeledvehicle 450. Accordingly, the guard members 462 and 464 can pivot withrespect to the chassis 452 as the wheel 454 moves up and down. In someembodiments, the suspension 456 includes an axle 455 and a spring 457connecting the axle 455 to the chassis 452. In some embodiments, thesecond end portions can be coupled to the axle 455. As shown in FIG. 10,the guard members 462 and 464 pivot about pivot axes (e.g., pivotmechanisms 466 and 468) substantially parallel with the axis (e.g., axle455) of the wheel 454.

Remarks

The above description and drawings are illustrative and are not to beconstrued as limiting. Numerous specific details are described toprovide a thorough understanding of the disclosure. However, in someinstances, well-known details are not described in order to avoidobscuring the description. Further, various modifications may be madewithout deviating from the scope of the embodiments. Accordingly, theembodiments are not limited except as by the appended claims.

Reference in this specification to “one embodiment” or “an embodiment”means that a particular feature, structure, or characteristic describedin connection with the embodiment is included in at least one embodimentof the disclosure. The appearances of the phrase “in one embodiment” invarious places in the specification are not necessarily all referring tothe same embodiment, nor are separate or alternative embodimentsmutually exclusive of other embodiments. Moreover, various features aredescribed which may be exhibited by some embodiments and not by others.Similarly, various requirements are described which may be requirementsfor some embodiments but not for other embodiments.

The terms used in this specification generally have their ordinarymeanings in the art, within the context of the disclosure, and in thespecific context where each term is used. It will be appreciated thatthe same thing can be said in more than one way. Consequently,alternative language and synonyms may be used for any one or more of theterms discussed herein, and any special significance is not to be placedupon whether or not a term is elaborated or discussed herein. Synonymsfor some terms are provided. A recital of one or more synonyms does notexclude the use of other synonyms. The use of examples anywhere in thisspecification, including examples of any term discussed herein, isillustrative only and is not intended to further limit the scope andmeaning of the disclosure or of any exemplified term. Likewise, thedisclosure is not limited to various embodiments given in thisspecification. Unless otherwise defined, all technical and scientificterms used herein have the same meaning as commonly understood by one ofordinary skill in the art to which this disclosure pertains. In the caseof conflict, the present document, including definitions, will control.

What is claimed is:
 1. An omnidirectional wheel mountable for rotationabout a wheel axis, comprising: a central disk assembly, including: acentral carrier plate having a first diameter; and a plurality ofcentral rollers each rotatably coupled to a circumferential margin ofthe central carrier plate for rotation about a first roller axisoriented orthogonal to the wheel axis; and a pair of lateral diskassemblies coaxially positioned on opposite sides of the central diskassembly, each lateral disk assembly including: a lateral carrier platehaving a second diameter smaller than the first diameter; and aplurality of lateral rollers each rotatably coupled to a circumferentialmargin of the lateral carrier plate for rotation about a second rolleraxis oriented orthogonal to the wheel axis.
 2. The omnidirectional wheelof claim 1, wherein the circumferential margins of the central andlateral carrier plates each include a plurality of notches configured toreceive a corresponding roller.
 3. The omnidirectional wheel of claim 1,further comprising a hub, wherein the pair of lateral carrier plates andthe central carrier plate are attached to the hub.
 4. Theomnidirectional wheel of claim 3, wherein the hub includes an axle boreextending along the wheel axis.
 5. The omnidirectional wheel of claim 1,wherein the lateral rollers are circumferentially offset from thecentral rollers.
 6. The omnidirectional wheel of claim 1, wherein thelateral rollers and the central rollers each have approximately the sameroller diameter.
 7. An omnidirectional wheel, comprising: a hubmountable for rotation about a hub axis, the hub including: a centraldisk portion having a central diameter; a first lateral disk portionhaving a first diameter; and a second lateral disk portion having asecond diameter; a plurality of central rollers each rotatably coupledto a circumferential margin of the central disk portion for rotationabout a central roller axis oriented orthogonal to the hub axis; aplurality of first rollers each rotatably coupled to a circumferentialmargin of the first lateral disk portion for rotation about a firstroller axis oriented orthogonal to the hub axis; and a plurality ofsecond rollers each rotatably coupled to a circumferential margin of thesecond lateral disk portion for rotation about a second roller axisoriented orthogonal to the hub axis.
 8. The omnidirectional wheel ofclaim 7, wherein the first and second diameters are smaller than thecentral diameter.
 9. The omnidirectional wheel of claim 8, wherein thefirst and second diameters are approximately equal to each other. 10.The omnidirectional wheel of claim 7, wherein the circumferentialmargins of the central, first lateral, and second lateral disk portionseach include a plurality of notches configured to receive acorresponding roller.
 11. The omnidirectional wheel of claim 7, whereinthe central, first lateral, and second lateral disk portions comprise aunitary body.
 12. The omnidirectional wheel of claim 7, wherein thefirst and second rollers are circumferentially offset from the centralrollers.
 13. The omnidirectional wheel of claim 7, wherein the firstrollers, the second rollers, and the central rollers each haveapproximately the same roller diameter.
 14. The omnidirectional wheel ofclaim 7, wherein the hub includes an axle bore extending along the wheelaxis.
 15. A mecanum wheel mountable for rotation about a wheel axis,comprising: a first hub disk having a first diameter and a plurality offirst roller mounts disposed around a circumferential margin of thefirst hub disk; a second hub disk having a second diameter smaller thanthe first diameter and a plurality of second roller mounts disposedaround a circumferential margin of the second hub disk; and a pluralityof rollers each extending between corresponding circumferentially offsetfirst and second roller mounts, whereby each of the plurality of rollersis mounted for rotation about a corresponding roller axis oriented at acompound angle with respect to the wheel axis.
 16. The mecanum wheel ofclaim 15, wherein each of the plurality of rollers is tapered from alarge end coupled to a corresponding one of the first roller mounts to asmall end coupled to a corresponding one of the second roller mounts.